US investigators join Mexico chopper crash probe

MEXICO CITY 
The U.S. National Transportation Safety Board has sent a team of investigators to Mexico to probe the helicopter crash that killed the country's No. 2 official.

The board says it has also sent representatives of the Federal Aviation Administration to investigate Friday's crash in a rural area south of Mexico City. The crash killed Interior Minister Francisco Blake Mora and seven others.

The safety board said in a news release Sunday that Mexico requested help. The agents arrived Saturday.

President Felipe Calderon has asked Mexico's transportation secretary to carry out a thorough investigation into the causes of the helicopter crash.

Mexico's Transportation and Communications Department will remain the lead investigative agency.